1. Technical Field
The present invention relates to a transceiver applied to a node having a sleep/wakeup function.
2. Related Art
Conventionally, a communication system is known which is installed in a vehicle and uses a bus communication line, such as CAN (Controller Area Network) and LIN (Local Interconnect Network) (refer to, e.g., “In-vehicle Network System Detailed Explanation” written by Michio Sato, CQ Publishing Co., Ltd, issued Dec. 1, 2005).
To perform efficient communication in this type of communication system, operations of transceivers provided in nodes for transmitting and receiving signals via a bus communication line are desired to be synchronized with each other.
In this case, any one of the nodes transmits a signal encoded with a transmission line code including a clock component to the bus communication line. The other nodes extract the clock component from the signal on the bus communication line, and process (e.g. divide) a free-running clock generated by the own transceiver. Thereby, the other nodes generate a bus clock synchronized with the extracted clock component to operate the transceiver according to the bus clock.
In addition, including the following function is considered. According to this function, in order to reduce the power consumption by the nodes configuring the communication system, if a predetermined sleep condition is met, the node shifts to a sleep mode which is an operation mode for stopping part of functions of the node. If a wakeup condition is met, or the output of a predetermined start signal to a communication line is detected, the node in the sleep mode shifts to a wakeup mode which is an operation made for operating all the functions of the node.
Meanwhile, if the node in the sleep mode is activated by using a start signal, the transceiver is required to be operated all the time regardless of the operation mode so that the start signal can be received all the time.
However, if the transceiver is operated continuously, a bus clock required for the operation of the transceiver and various timing signals synchronized with the bus dock are generated. Hence, even in the sleep mode, significant electric power is consumed.